In the oil and gas industry, wellbores are drilled into the earth using drilling rigs, where tubulars are threaded together to form long tubular strings that are inserted into the wellbore to extract the desired fluid. The tubing string is generally suspended in the borehole using a rig floor-mounted spider or slips, such that each new tubular segment or stand may be threaded onto the end of the previous tubular just above the spider. A single joint or stand elevator, such as that disclosed by U.S. Pat. No. 8,141,923, which is incorporated herein by reference, is commonly used to grip and secure the segment or stand to a hoist to lift the segment or stand into position for threading the tubular together. A compensator, such as that disclosed by U.S. Pat. No. 6,000,472, which is incorporated herein by reference, is generally used in combination with single joint or stand elevators to reduce the weight of the stand on the connection of the previous string. Once set into position the tubular is rotated with a power tong and the entire elevator is allowed to rotate with the aid of a swivel to facilitate the threading of the connection. Once the connection is threaded a string elevator is used to lower the string to the rig floor. Once lowered the spider or slips are activated to suspend the string once more. This process continues until the required number of tubing segments have been lowered into the well.
In general, single joint or stand elevators are specifically adapted for securing and lifting tubular segments having a conventional connection, such as an internally threaded sleeve that receives and secures an externally threaded end from each of two tubular segments to secure the segments in a generally abutting relationship. And compensators are specifically adapted to the system to permit controlled maneuverability of the segment to eliminate costly damage to the lifted segment, the segment in the spider, or operational efficiency. Also, swivels are employed to allow rotation of the elevator thus giving the ability to rotate and secure the tubular segments in said relationship.
Most single joint or stand elevators are suspended below the string elevator using cables, a swivel and one or two compensating rams in parallel. This method of using compensating rams to hold up the single joint elevator may have great safety consequences. Should the compensating ram or rams fail it is possible to drop the elevator and tubing to the rig floor. To reduce the safety concern most compensating rams are fitted with safety cables to prevent the elevator from falling. However, there are still safety concerns due to the stand of tubulars swinging violently should one of the compensating rams fail.
At least one challenge encountered by tubular running companies is maintaining proper thread integrity of the connections while making up the stand to the string of tubulars. Generally, if the threads of the two connecting tubulars are not properly aligned and then engaged when the rotation of the make-up string with power tongs begins, the threads of both connections will usually gall or be crushed to a state of non-compliance with industry standards. This result may also occur when too little or excessive weight is applied by the hoisted segment onto the segment secured by the spider. Typically these connections will have to be removed from the string and discarded or sent back to the manufacturer to be re-threaded. This removal of tubulars and connections from the string can be time consuming and very costly to the rig operator.